As disclosed in Patent Literature 1, induction heated roll apparatuses include one that directly measures temperature with a temperature detecting element attached to a roll main body as a heated body.
Meanwhile, a roll main body is a rotating body, and therefore in many cases, it is not easy to attach a temperature detecting element. Also, in the case of attaching a temperature detecting element to a roll main body, a contact state between the temperature detecting element and the roll main body is individually different, which may cause an error in detected temperature. Further, in order to input an output from a temperature detecting element provided in a roll main body to a fixed control device, a sophisticated device such as a rotary transformer is required.
In addition, it is also possible to use non-contact type temperature detecting means such as a radiation pyrometer to detect the temperature of a roll main body; however, in such a case, it is often difficult to detect an accurate temperature because detection accuracy is low or the temperature is affected by a surface radiation rate (emission rate) of the roll main body.